The pig is a natural host for Schistosoma japonicum and a useful animal model of human infection. The aim of the present study was to assess the differences between the cytokine profiles in prenatally or postnatally S. japonicum exposed pigs. Seven prenatally exposed pigs, 7 postnatally exposed pigs and 4 uninfected control pigs were compared 27 weeks post exposure. Variables included worm burdens, tissue egg counts, liver pathology and mRNA levels of IL-2, IL-4, IL-10, IL-12, TNF-alpha, TGF-beta 1 and IFN-gamma in the liver and the caecum, assessed by RT-PCR. Infection intensity and level of septal fibrosis were significantly higher in the postnatal group compared to the prenatal group (P <0.05). A significant increase of IL-4 (P <0.01), IL-10 (P <0.01), IL-12 (P <0.01) and TNF-alpha (P <0.05) mRNA level was also observed in the caecum of prenatally infected animals compared to the control group (P <0.01). The prenatal group showed higher levels of TGF-beta 1 in the liver compared with the postnatally infected group (P <0.05) and the control group (P <0.01). This suppressive immune response correlated with previously reported low hepatic pathogenesis in prenatally exposed pigs.